The present invention relates generally to high speed pluggable connectors, and more particularly, to shielded, pluggable connectors with improved cooling capabilities.
Moore's Law, which is more properly termed an observation, is based on the understanding that in the field of integrated circuits, the complexity (or number of circuits) will double every two years. The fact that this observation has held true since about 1965 has had a remarkable impact on the world as we know it. Computation speeds that were in the realm of science fiction have become a reality. Moore's Law, as it is known, continues and while there appear to be fundamental physical limits to how small an integrated circuit can be made, other technologies may provide substitutes that allow the effect (the doubling of performance every two years) to continue for the foreseeable future.
One consequence of the increase in performance is that data needs to be transmitted at increasing rates. Data transmission rates that were unthinkable just a few years ago are a current reality and faster data transmission speeds are being planned into next generation products. For example, current data transmission rates that are used in the telecommunications industry are 12 to 15 Gbps (gigabits/second) and rates of 25 to 30 Gbps are already on the horizon. The increase (or desire for an increase) in data transmission rates affects the entire data infrastructure. For example, as part of their computer network companies will often employ servers and routers (which may be referred to as data-handling devices) so that computers in the company can communicate and access data in a desirable manner. These data-handling devices can be connected together by cable assemblies which utilize two plug connectors terminated to a length of cable. The plug connectors often take the form of electronic, pluggable modules that are inserted into an opening in the data-handling devices so as to mate with and engage an opposing mating connector. Within the data-handling devices, connectors are mounted to a circuit board and a cage typically surrounds the connector. The cage defines a hollow enclosure that envelops the component connector and within the enclosure, a module-receiving channel or bay is defined so that a module can be inserted into the channel. In operation, this allows the two data-handling devices to communicate with each other at high data rates.
The shielding provided by the cage is used to reduce electromagnetic interference (EMI) that may be emitted, for example, from other nearby connectors. Because of the high frequencies used to transmit the date, it is desirable to make the cage continuous so that no openings are provided to allow for high-frequency signals to enter and affect the intended signals moving through the connectors. However, with the increase in shielding comes a resultant poor airflow over the module. This lack of air-flow can create problems because at higher data rates the amount of energy passing through the connector increases and the increased energy increases the amount of heat that the connector has to dissipate. While the use of a heat sink has helped address this heat dissipation issue, one configuration that has been difficult to address is a stacked connector configuration is used. While air can be directed over the top of a stacked connector (the top of which can readily include a heat sink with fins to help dissipate heat), the lower connector is effectively sandwiched between an insulating circuit board and a heat generating module, making cooling particularly challenging. A known solution to this type of problem has been to mount the connectors belly to belly with heat sinks on opposite sides of the cages. As can be appreciated, however, this creates problems in plugging in modules because some modules will need to be turned upside down and it can be difficult to tell which way to turn the module when a person is facing a number of rows of such connectors. Furthermore, the split orientation of the connectors limits the interface with the circuit board that supports the connectors. Therefore, improvements in connector designs that could accommodate high heat loads would be appreciated.